JPH04246617A - Optical fiber collimator - Google Patents

Abstract

PURPOSE:To facilitate the centering of a spherical lens and a ferrule with a fiber at the time of fixing the spherical lens and the ferrule in a sleeve and to facilitate positioning and fixing at the time of combining the same with an optically passive element or optically active element. CONSTITUTION:The through-hole of the sleeve 12 is made into a stepped structure in which a small-aperture diameter part 20 having the diameter nearly equal to the outside diameter of the ferrule 16 and a large-aperture diameter part 22 larger than the outside diameter of a drum lens 18 continue with an intermediate step part 24 as a boundary. The spherical part of the drum lens is fixed by low melting glass 26 in the state of pressing this part to the edge 24a of the intermediate step part in the large-aperture diameter part and the ferrule with the fiber is inserted into the small-aperture diameter part and is fixed in the position where the end face of the fiber matches the focal length of the lens.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber collimator in which a spherical lens and a ferrule with a fiber are fixed within a sleeve. More specifically, the present invention relates to an optical fiber collimator in which a step is formed in a through hole of a sleeve, and a spherical lens is brought into contact with the edge of the step to align the centers of the spherical lens and the ferrule. This optical fiber collimator is used for emitting and condensing parallel light in fields such as optical communication, optical measurement, and optical recording.

0002

2. Description of the Related Art A collimator using an optical fiber is constructed by inserting and fixing a lens and a ferrule with a fiber into a cylindrical sleeve. At that time, the positions of both are adjusted so that the fiber end face matches the focal length of the lens. The through hole of the sleeve is a straight hole having the same cross-sectional shape over the entire length of the sleeve, and its diameter is made approximately equal to the outer diameter of the lens and the ferrule. Here, as the lens, a gradient index rod-shaped microlens, a spherical lens made of glass or plastic, etc. are used, and the lens is fixed to the sleeve by press-fitting or by using an adhesive or the like.

However, at present, the gradient index rod-shaped microlens has the problem of a low condensing efficiency and a large coupling loss, and therefore it is considered better to use a glass ball lens with a small parallel beam diameter. Also, the ball lens is 1μ
Since it can be processed with an accuracy of about m, if a spherical lens is used, the center of the spherical surface of the lens can be aligned with the center of the ferrule, and the parallel light will be emitted parallel to the optical axis. This is because positioning and assembly becomes easier when converting.

0004

However, when using a spherical lens, it is not always easy to align the center of the spherical surface of the lens with the center of the ferrule within the sleeve. This is because it is undesirable to press fit the ball lens into the sleeve. If the sleeve becomes thicker due to press-fitting, dimensional accuracy will decrease (the center of the sleeve will be misaligned with the center of the spherical lens surface), and even if the sleeve does not deform, excessive stress will change the lens characteristics if excessive stress is applied to the lens. It is from.

It is also possible to use a so-called drum lens, which is a cylindrically ground spherical lens, as the spherical lens, but in that case, it is necessary to grind the lens so that the center of the spherical surface of the lens coincides with the center of the outer peripheral surface (drum surface) of the lens. This is difficult, and it is usually unavoidable that a deviation of about 50 μm occurs. Incidentally, since the ferrule can be machined with an accuracy of 1 μm or less, and the sleeve can also be machined with an accuracy of about 4 μm, using a drum lens in the conventional technology results in a significant decrease in the final assembly accuracy of the optical fiber collimator.

An object of the present invention is to solve the problems of the prior art as described above, and to easily align the center of the spherical surface of the lens with the center of the ferrule. An object of the present invention is to provide an optical fiber collimator that can emit light. Another object of the present invention is to provide an optical fiber collimator that can be easily positioned and fixed when combined with an optical passive element or an optical active element.

[0007]

SUMMARY OF THE INVENTION The present invention is an optical fiber collimator in which a spherical lens and a ferrule with a fiber are fixed within a sleeve. In order to achieve the above object, in the present invention, the through hole of the sleeve has a small diameter part that is approximately equal to the outer diameter of the ferrule, and a large diameter part that is larger than the outer diameter of the spherical lens, which are continuous with an intermediate step part as a boundary. It has a stepped structure. Then, a spherical lens is fixed in the large diameter part of the sleeve with the lens spherical surface in contact with the edge of the intermediate stepped part, and a ferrule with a fiber is inserted into the small diameter part to a position where the fiber end surface matches the focal length of the lens. The ferrule is fixed to the sleeve.

Here, a drum lens obtained by cylindrical grinding of a glass spherical lens is used as the spherical lens, and a low melting point glass is filled between the outer peripheral surface of the drum lens and the inner peripheral surface of the large diameter part of the sleeve and fixed. It is preferable.

[0009]

[Operation] The small diameter part of the sleeve is set to be approximately equal to the outer diameter of the ferrule (with enough dimensional accuracy to allow insertion), so by inserting the ferrule into the small diameter part, the center of the ferrule (optical fiber center axis of the core)
) corresponds to the center of the small diameter part of the sleeve. When the spherical lens surface hits the edge of the intermediate stepped portion, the center of the spherical lens surface (for example, the spherical center in the case of a spherical lens) automatically coincides with the center of the small diameter portion of the sleeve. The alignment of the center of the lens spherical surface is determined by the edge of the intermediate stepped portion, and is not affected by the shape of the large diameter portion or the deviation of the center.

As a result, the center of the ferrule and the center of the lens coincide, and by moving the ferrule in and out of the small diameter part of the sleeve and fixing it at a position where the fiber end surface matches the focal length of the lens, the light is directed parallel to the optical axis. Emits light. By increasing the accuracy of the parallelism between the small diameter portion of the sleeve and the outer surface, parallel light parallel to the sleeve surface can be obtained.

Even if the diameter of the spherical lens varies, it is possible to use the spherical part to align the center as described above, and if a drum lens is used as the spherical lens, chucking can be performed on the outer peripheral surface. There is also the advantage that a spherical anti-reflection coating can be applied. By using low melting point glass to fix the glass spherical lens, more reliable fixation is possible.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing an embodiment of an optical fiber collimator according to the present invention, and FIG. 2 is an explanatory diagram of its assembly. This optical fiber collimator 10 has a structure in which a ferrule 16 with an optical fiber 14 and a drum lens 18 are fixed in a sleeve 12 having a substantially cylindrical shape. Here, the fiber-attached ferrule 16 is made by gluing and fixing a part of the optical fiber 14 at the center of the ferrule 16.
The drum lens 18 is a cylindrically ground spherical lens made of optical glass BK7 or the like.

The present invention is characterized by the shape of the through hole of the sleeve 12 and the positioning structure of the drum lens 18. Sleeve 12 is made of stainless steel. The through hole of the sleeve 12 has a small diameter part 20 that is approximately equal to the outer diameter of the ferrule 16 halfway through, and a large diameter part 22 that is larger than the outer diameter (diameter of the outer peripheral surface) of the drum lens 18 after the middle. , which has a continuous stepped structure with the intermediate stepped portion 24 as a boundary. The intermediate step portion 24 is formed perpendicularly to the central axis of the sleeve 12. And the large diameter portion 22 of the sleeve 12
The drum lens 18 is attached to the edge 24a of the intermediate stepped portion 24 within the
The spherical portion (lens spherical surface 18a) of the drum lens 18 is brought into contact with the drum lens 18, and the drum lens 18 is fixed in this state. This fixation is performed by filling the annular gap between the lens outer circumferential surface 18b and the inner circumferential surface of the large diameter portion 22 of the sleeve 12 with low melting point glass 26.

[0014] Then, the ferrule 16 with a fiber is inserted into the small diameter portion 20, and the ferrule 16 and the sleeve 12 are fixed by laser welding or the like at a position where the end face of the fiber matches the focal length f of the lens. The welded portion is designated by the reference numeral 28.

The small diameter portion 20 of the sleeve 12 is approximately equal to the outer diameter of the ferrule 16 (strictly speaking, the outer diameter of the ferrule 16
(outer diameter of the sleeve + 4 μm or less), by inserting the ferrule 16 into the small diameter portion 20, the center of the ferrule 16 (the central axis of the core of the optical fiber 14) is aligned with the small diameter portion of the sleeve 20. Match the center. As mentioned above, the thickness of the optical fiber 14 and the ferrule 16 is 4 μm.
This is because it can be combined with the following accuracy. Then, when the lens spherical surface 18a is brought into contact with the edge 24a of the intermediate step portion 24,
The center of the lens spherical surface 18a automatically coincides with the center of the small diameter sleeve portion 20. The alignment of the center of the lens spherical surface 18a is defined by the edge 24a of the intermediate stepped portion 24, and is independent of the shape of the large diameter portion 22 and the central axis. In other words, the large diameter portion 22 and the small diameter portion 20 do not need to be concentric or parallel. Further, it is not necessary that the center of the lens spherical surface 18a and the center of the lens outer circumferential surface 18b coincide with each other.

As a result, the center of the ferrule and the center of the drum lens (the center of the spherical lens surface) coincide, so that when the ferrule 16 is moved in and out of the small-diameter sleeve portion 20, the fiber end face matches the focal length of the drum lens 18. When fixed at , the light is emitted parallel to the optical axis. Sleeve 12
By increasing the accuracy of the parallelism between the small diameter portion 20 and the outer surface of the sleeve 12, parallel light parallel to the side surface of the sleeve 12 can be obtained.

Since the drum lens 18 is used in this embodiment, the outer peripheral surface 18b of the lens can be used for chucking, and the spherical surface 18a of the lens can be coated with a non-reflective coating. Further, an annular gap is created between the lens outer circumferential surface 18b and the inner circumferential surface of the large diameter portion 22, which can be used for filling the low melting point glass 26. By using low melting point glass, more reliable fixing is possible.

Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above configuration. The lens shape may have at least a spherical portion in a portion (the portion facing the small diameter portion), and the other portion may have a circumferential surface or a shape that is ground flat. The intermediate stepped portion formed on the sleeve may be a surface perpendicular to the central axis of the sleeve, or may be a conical surface having a certain angle.

[0019]

[Effects of the Invention] As described above, the optical fiber collimator of the present invention has a configuration in which the spherical lens is aligned by abutting against the edge of the intermediate stepped portion of the sleeve, so that the center of the spherical lens surface and the center of the ferrule can be easily aligned. be able to. Therefore, parallel light parallel to the optical axis can be emitted, improving the workability of assembly and adjustment. In addition, the optical fiber collimator of the present invention can be combined with an optical passive element or an optical active element, since parallel light parallel to the side surface of the sleeve can be obtained by increasing the accuracy of parallelism between the small diameter part of the sleeve and the outer surface. Positioning and fixing can be easily performed.

When a drum lens is used as the spherical lens, an anti-reflection coating can be easily formed on the spherical part,
It can be fixed to the sleeve using low melting point glass using the outer peripheral surface.
Reliability is also improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of an optical fiber collimator according to the present invention.

FIG. 2 is an explanatory diagram for assembling the optical fiber collimator of FIG. 1;

[Explanation of symbols]

10 Optical fiber collimator 12 Sleeve 14 Optical fiber 16 Ferrule 18 Drum lens 20 Small diameter part 22 Large diameter part 24 Intermediate step part 26 Low melting point glass

Claims (2)

[Claims] 1. An optical fiber collimator in which a spherical lens and a ferrule with a fiber are fixed within a sleeve, wherein the through hole of the sleeve has a small diameter portion approximately equal to the outer diameter of the ferrule and a diameter larger than the outer diameter of the spherical lens. The large diameter part has a continuous stepped structure with the intermediate step part as a boundary, and the spherical lens is fixed within the large diameter part of the sleeve with the lens spherical surface in contact with the edge of the intermediate step part, and the small diameter part An optical fiber collimator characterized in that a ferrule with a fiber is inserted into the ferrule and the ferrule is fixed at a position where the end face of the fiber matches the focal length of the lens, so that the center of the spherical surface of the lens coincides with the central axis of the core of the optical fiber. 2. A claim in which the spherical lens is a drum lens obtained by cylindrical grinding of a glass spherical lens, and a low melting point glass is filled and fixed between the outer circumferential surface of the drum lens and the inner circumferential surface of the large diameter portion of the sleeve. 1. The optical fiber collimator according to 1.